Tim Bosma (pictured) was reported missing Monday night after two men arrived at his home for a test drive of his black 2007 Dodge Ram pickup, which Bosma had listed for sale online. (Hamilton Police) | Hamilton Police

HAMILTON - Police are readying search warrants and say they are entering "critical hours" after the arrest of a suspect in connection with the disappearance of a southwestern Ontario man who went missing after taking two men for a test drive of his truck.

Hamilton police Supt. Dan Kinsella said that a massive search involving more than 150 police officers has not located Tim Bosma as of Saturday afternoon. Bosma, 32, vanished Monday night after leaving his Hamilton home with a pair of men who responded to an online ad for his black 2007 Dodge Ram pickup.

Kinsella said Saturday that one of two male suspects sought in the case was arrested without incident while driving in Mississauga, west of Toronto. The second suspect has not been identified and did not say whether the arrested man is co-operating with police, Kinsella said.

"We are encouraged with the progress of our investigation and must be cautious in our approach over the next few critical hours," he said.

"Our greatest priority is the welfare and locating of Tim Bosma."

Kinsella said search warrants were being drawn up, but offered scant few details about the case, which he said was changing "minute by minute."

"Information is being obtained, search warrants are being prepared and evidence is being gathered."

Kinsella declined to comment whether Bosma's truck has been found.

He said the suspect picked up by police was identified by a tattoo on his wrist investigators have called "unique" — the word "Ambition" framed by a box.

Toronto resident Dellen Millard, 27, is charged with forcible confinement and theft over $5,000. It was not immediately known when the suspect was to appear in court.

The arrest comes after a police search found Bosma's cellphone Thursday afternoon in an industrial area in nearby Brantford, a development that gave investigators a record of phone calls they say let them hone in on a phone used by the suspects to contact Bosma about his truck ad.

Kinsella said the communications trail then led them to a Toronto man who had earlier given the two suspects a test drive of his own Dodge Ram truck posted for sale online, and gave police the key detail of the wrist tattoo.

He said the suspect now charged by police is believed to have been behind the wheel of that truck tryout, which occurred one day before Bosma's disappearance but ended without incident, though the seller later told police the two men were "suspicious."

Officers from multiple police services are using K-9 units to scour through ground in the Brantford area. Kinsella said investigators have "relentlessly pursued" more than 300 tips sent along to police, who have set up a hotline solely for the Bosma case.

Police have described the second suspect as white, in his early 20s, around 5-foot-9 with a small-to-medium build and dark hair. They say he was seen wearing a red-hooded sweatshirt with the hood pulled over his head.